Anything as long as you are close to the weight limit, most don't mind a bit of flex over. As others have said getting clothes/shoes in etc is a good idea to save in your hand luggage.
Invest in a decent travel bag and get a padlock to be safe. I have packed a magnum of champagne (raffle prize not comp lol) in mine before as couldn't take on as hand luggage!!
Having flown a few times with my golf clubs I would advise sticking as much clothing, etc, into your travel bag.
All the airlines are bothered about is the weight, so get it just under the weight and you will be good to go.
Also, putting clothing around your clubs is an extra level of protection from damage.
I managed to get all my clothing into my golf bag for my last trip.
Then, I used hand luggage to take anything else I needed.